Maîtrise par l’alimentation des teneurs en acides gras et en composés vitaminiques du lait de vache

This paper, after summarising the digestive and metabolic origins of milk fatty acids and vitamins, presents the effects of the main nutritional factors on their concentration. Grazed grass, when compared to winter diets, decreased the milk content of saturated fatty acids, in favor of trans and polyunsaturated fatty acids, including C18:3n-3 and c9t11-CLA. Short- and long-term supplementation of dairy cow diets with linseed or rapeseed increased the milk content of trans fatty acids and slightly c9t11-CLA. Cows fed linseed produced milks richer in C18:3n-3 and poorer in c9-C18:1 than those fed rapeseed. The responses depend on interactions among the nature of the forage, starch content and oilseed nature. The addition of tannins or essential oils has little influence on milk fatty acid composition. Except for the B12 vitamin, all vitamins present in milk can originate from forages or concentrate, and/or mineral premix containing A, E and D3 vitamins. The ruminant can also synthesize A, C, B3, and D vitamins from dietary precursors. The B and K vitamins are synthesized by rumen bacteria. The nutritional factors altering milk vitamin concentrations are not well documented, except for vitamin A. Nevertheless, feeding is an important tool to improve milk nutritional quality.